0 /4 * * — what this cron expression means

The cron expression 0 */4 * * * runs every 4 hours on the hour. Here is the field-by-field breakdown and what it means in plain English.

Cron expression (minute hour day-of-month month day-of-week)

What 0 /4 * * means

It runs every 4 hours, on the hour: 00:00, 04:00, 08:00, 12:00, 16:00 and 20:00.

minute=0, hour=*/4 (a step every 4 hours starting at 0), day/month/day-of-week all *.

Six runs a day, evenly spaced four hours apart.

Next run: the next matching time for 0 */4 * * *.

At 00:00, 04:00, 08:00, 12:00, 16:00 and 20:00 — six times a day.

Yes, with minute=0 it fires at the top of every fourth hour from midnight.